System.Web.HttpContext.Current.Response.ContentType = "application/pdf";
            System.Web.HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
            System.Web.HttpContext.Current.Response.AddHeader("Content-disposition", string.Format("attachment; filename={0}", fileName));
            System.Web.HttpContext.Current.Response.OutputStream.Write(memoryStream.GetBuffer(), 0, memoryStream.GetBuffer().Length);
            System.Web.HttpContext.Current.Response.OutputStream.Flush();
            System.Web.HttpContext.Current.Response.OutputStream.Close();
这段代码怎么改为将pdf文件自动保存指定文件夹呀？